linux-kernel - RE: [PATCH v6 04/10] scsi: ufs: introduce UFSHCD_QUIRK_PRDT_BYTE

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Message-ID: <000101d61be3$362e79f0$a28b6dd0$@samsung.com>
Date:   Sun, 26 Apr 2020 21:26:08 +0530
From:   "Alim Akhtar" <alim.akhtar@...sung.com>
To:     "'Christoph Hellwig'" <hch@...radead.org>
Cc:     <robh@...nel.org>, <devicetree@...r.kernel.org>,
        <linux-scsi@...r.kernel.org>, <krzk@...nel.org>,
        <avri.altman@....com>, <martin.petersen@...cle.com>,
        <kwmad.kim@...sung.com>, <stanley.chu@...iatek.com>,
        <cang@...eaurora.org>, <linux-samsung-soc@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v6 04/10] scsi: ufs: introduce
 UFSHCD_QUIRK_PRDT_BYTE_GRAN quirk

Hi Christoph,

> -----Original Message-----
> From: Christoph Hellwig <hch@...radead.org>
> Sent: 22 April 2020 12:24
> To: Alim Akhtar <alim.akhtar@...sung.com>
> Cc: robh@...nel.org; devicetree@...r.kernel.org;
linux-scsi@...r.kernel.org;
> krzk@...nel.org; avri.altman@....com; martin.petersen@...cle.com;
> kwmad.kim@...sung.com; stanley.chu@...iatek.com;
> cang@...eaurora.org; linux-samsung-soc@...r.kernel.org; linux-arm-
> kernel@...ts.infradead.org; linux-kernel@...r.kernel.org
> Subject: Re: [PATCH v6 04/10] scsi: ufs: introduce
> UFSHCD_QUIRK_PRDT_BYTE_GRAN quirk
> 
> On Fri, Apr 17, 2020 at 11:29:38PM +0530, Alim Akhtar wrote:
> > Some UFS host controllers may think granularities of PRDT length and
> > offset as bytes, not double words.
> >
> > Signed-off-by: Kiwoong Kim <kwmad.kim@...sung.com>
> > Signed-off-by: Alim Akhtar <alim.akhtar@...sung.com>
> > ---
> >  drivers/scsi/ufs/ufshcd.c | 30 +++++++++++++++++++++++-------
> > drivers/scsi/ufs/ufshcd.h |  6 ++++++
> >  2 files changed, 29 insertions(+), 7 deletions(-)
> >
> > diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> > index ee30ed6cc805..b32fcedcdcb9 100644
> > --- a/drivers/scsi/ufs/ufshcd.c
> > +++ b/drivers/scsi/ufs/ufshcd.c
> > @@ -2151,8 +2151,14 @@ static int ufshcd_map_sg(struct ufs_hba *hba,
> struct ufshcd_lrb *lrbp)
> >  		return sg_segments;
> >
> >  	if (sg_segments) {
> > -		lrbp->utr_descriptor_ptr->prd_table_length =
> > -			cpu_to_le16((u16)sg_segments);
> > +
> > +		if (hba->quirks & UFSHCD_QUIRK_PRDT_BYTE_GRAN)
> > +			lrbp->utr_descriptor_ptr->prd_table_length =
> > +				cpu_to_le16((u16)(sg_segments *
> > +					sizeof(struct ufshcd_sg_entry)));
> > +		else
> > +			lrbp->utr_descriptor_ptr->prd_table_length =
> > +				cpu_to_le16((u16) (sg_segments));
> 
> No double words here.  "Normal" UFS uses the actual segment count, while
> Samsumg uses bytes.  Also no need fo the u16 count in either the old or
new
> version.
Ok, will update the commit message and take your suggestion in the next
version.